Electric plug and socket



Sept. 29, 1942. J. JOYCE 2,297,188

ELECTRIC PLUG AND SOCKET Filed April l5, 1940 Patented Sept. 29, 1942UNITED STATES PATENT OFFICE ELECTRIC PLUG AND SOCKET John Joyce,Dorchester, Mass.

Application April 15,' 1940, Serial No. 329,618

Claims.

This invention relates to electric connectors or plugs adapted toconnect an electric device with an electric circuit; and to sockets orreceptacles adapted to receive the plug, and especially to a plug havingmultiple terminals connected to different voltage windings of anelectrical device.A

'I'here are electrical devices having plural windings or circuitsdesigned for different voltages, any one winding or circuit of which isdesigned to operate the device satisfactorily when energized at itsdesigned voltage.

One of the objects oi the present invention is the provision of a plugadapted to enter at will any one of a plurality of appropriate socketsenergized at different voltages and automatically connect the socketterminals only with the winding or circuit of the associated device thatis designed for operation on the voltage oi the selected socket.

An electric razor, for instance, is normally designed for operation on110 volts, which is the standard house voltage. The owner of the razor,however, would like to carry the razor on his travels and to use it onPullman trains, airplanes and automobiles. The voltages of the electriccircuits of these various conveyances, however, are diierent, 32 voltsbeing common on railroad trains, also farm lighting plants, 12 voltsbeing commonly used in airplanes, and 6 volts in automobiles. Electricrazors have been proposed having windings and switches so arranged thatby properly setting a control switch the razor would v be conditionedfor operation at any one oi a plural number of diierent voltages. Theobjection to this arrangement, however, is that the user forgets to setthe switch for the proper voltage and it is possible to plug the razorinto a 110 volt circuit; for instance. with the razor set for operationon a lowex` voltage, thereby burning out an energizing winding.

It thus is an object of the present invention to provide an electricalappliance having multiple windings or circuits adapted for operation ondifferent voltages with an attachment plug having terminals connected tothe various circuits and so arranged that while the plug can be pluggedinto appropriate sockets energized at different voltages it can onlyestablish a connection between the socket conductors and the appliance.circuit that is intended for operation upon the voltage of the socket.

A further object of the invention is the provision oi a plug having atleast three terminals adapted for connection with circuits designed fordifferent voltages, together with a socket adapted to receive the plugand having two terminals arranged to be connected wtih a circuit of aselected voltage, the plug and the socket being so arranged that onlythe terminals of the plug connected to a circuit designed for thevoltage applied to the terminals of the socket can be electricallyconnected with such socket terminals.

Another object of the invention is the provision of a plug having atleast three terminals, the plug and the terminals being so constructedand arranged that the plug can be inserted in the present-day socketthat. is standard for volts and the plug will have only its 110 voltterminals electrically connected with the socket terminals, the plugalso being so arranged as to be received in a diiierent socket havingterminals energized at a different voltage with only .the appropriateplug terminals in engagement with the terminals of such differentsocket.

A yet further object of the invention is the provision oi a plug havingtwo projecting terminals and a third terminal which can yield in thedirection of insertion of the plug so as to permit the plug to enter thepresent-day 110 volt socket and also to engage a properly disposedterminal of a different voltage socket.

Another object oi the invention is the provision of a socket havingprovision for receiving a contact or terminal member in any selected oneof at least two different positions corresponding with two differentvoltages.

Another object of the invention is generally to improve the constructionof plugs and sockets.

Fig. 1 is a perspective view of a multi-circuit plug embodying thepresent invention and provided with three terminals adapted forconnection with two circuits of different voltages.

' Fig. 2 is a sectional view taken along line 2-2 of Fig. l.

Fig. 3 is a sectional view of the plug of Fig. 1 taken at right anglesto the section of Fig. 2 or along line 3-3 of Fig. l.

Fig. 4 is a section similar to Fig. 2 but illustrating a modied form ofthe third terminal.

Fig. 5 is a section taken through the axis of a socket or receptacleadapted for cooperation with the plug of Figs. 1 and 2.

Fig. 6 is a sectional view taken at right angles to the showing of Fig.5 and corresponding with the View of the plug shown in Fig. 3.

Fig. 7 is a sectional view of a modified form of socket adapted forcooperation with the modified form of plug illustrated in Fig. 4.

Fig. 8 is an end or bottom view of the socket illustrated in Figs. 5, 6and 7.

Fig. 9 is a perspective view of a modified form of plug having fourterminals.

. Fig. 10 is an end or top view of the socket of Fig 5.

Fig. 11 is a circuit diagram illustrating the connections between themultiple windings of a power consuming device and the terminals of theplug of Fig. l.

Fig. 12 is a circuit diagram similar to Fig. 11

but illustrating the connections between multiplecircuits and theterminals of the plug of Fig. 9.

Fig. 13 is a sectional view similar to Fig. 2 but illustrating a furthermodiiied form oi low voltage terminal.

The plug embodying the present invention, in the three-terminal formillustrated in Fig. 1, comprises an insulating body I 0, that can begenerally cylindrical in form and has a flat terminal end I2. A pair ofterminals of the wiping contact type in the form of straight at bladesId and I6 project from said face in spaced relation with each other andwith the :dat faces parallel. The spacing between the blades, and thecrosssectional dimensions of the blades does not exceed thecorresponding dimensions of the usual two-blade plug adapted forinsertion in the present usual or standard 110 volt socket. Hence thepresent plug can be inserted inthe usual 110 volt socket and establishconnection with the socket terminals thereof. One of the blades, as theblade I4, is narrower, or has a. smaller cross-sectional dimension, thanthe otherblade I6 thereby to polarize the plug and prevent its beinginserted in a special socket presently to be described, except in apredetermined manner, whereby to preventimproper connections between theplug and socket terminals.

`The plug of Fig. 1 also is provided with a third terminal I8,preferably of the butt contact type, which is located below and betweenthe terminal blades I4 and I6. Said third terminal is yieldinglysupported so that it can move inwardly of the plug body when engagedwith a third terminal of the special lower voltage socket to bedescribed or when engagedwith some' projecting part of a standard 110volt socket, to permit effective entrance of the blades I4 and I6 intoeither socket.

As illustrated in all iigures but Fig. 4, the end or contact face ofsaid third terminal I8 is generally iiush with the end face I2 of theplug. Said terminal I8 comprises a cylindrical block which is slidablylocated in a, preferably, insulating tube 26, which may be made offibre, with the longitudinal axis of the tube generally parallel withbut oifset from the longitudinal axis of the plug. The inner end of thetube is closed by a metal end c ap 22 xed thereon. A exible conductor 24connects the end cap with the terminal block I8 and the length of theconductor is such that, when taut, it holds the terminal block with itsouter or contact face generally ush with the end face I2 of the plug.A-helical compression spring 26 is located Within the tube 20 about theconductor and bears at one end on the inner face of the end cap and atthe other end against the inner face of the terminal block I8, therebynormally holding the conductor straight and taut. Thus the free ordisengaged position of the third terminal is deined. Endwise pressure-on the contact face of the terminal block causes the spring to yieldand permit the block to move inwardly.

The method of anchoring the terminals in' the plug body is not ofimportance herein. A quite 75.

satisfactory method is to solder the terminals I4 and I6 to the ends ofinsulated conductors 28 and I having, say, a 12 volt winding 38V and a110 volt winding 40, which, with the connections illustrated, includesthe lower voltage winding. Energization of the terminals i6 and i8energizes the low voltage winding only, and energization of theterminals I6 and I4 energizes the high voltage winding. The differentwindings can be entirely separate as illustrated in Fig. 12, but someeconomy of wire and space is obtained byhaving the higher voltagecurrent pass through the lower voltage winding or windings. vention isconcerned, however, the more important object is to prevent a lowvoltage winding from being connected with a high voltage energizingcircuit so that the winding receives excessive current. l

A receptacle or socket adapted for cooperation with the abovedescribedplug is illustrated in Figs. 5, 6, 8 and 10. The socket includes a body42 which can be of insulating material and tubular and has a transversewall 44 of insulating material intermediate its ends and a forwardlyprojecting rim 46 forming a .tubular recess adapted to be entered by theplug. The outer end face of the wall which confronts the end face of theplug is generally iiat, preferably, and the wall is formed with slots oropenings 48 and 50 therethrough adapted to be entered by the plug.terminals I4 and I6, respectively. The slot 48 is transversely shorterthan the corresponding dimension of the slot 50 and the cross-sectionaldimensions of the slots `conform closely to the corresponding dimensionsof theplug .terminals I4 and I6. Thus the plug terminal I6 cannot enterthe slot 48 and hence the location of the third plug terminal I8 withrespect to the socket is assured. The rear face of the wall 44 isprovided with uitable resilient contact fingers 5I and 52 which are inposition to -be engaged and wiped over by the plug terminals I4 and I6,respectively, the fingers having terminal parts 54 and 56 either ofwhich can be connected with an energizing conductor. If the socket wereto be used on a volt circuit both parts would be provided with aconductor clamping screw 58 as shown screwthreaded in the terminal part56. Since, however, the socket is intended primarily for use with lowervoltages only one of the terminal parts and particularly the .terminalpart associated with the broader plug terminal I6 is provided with sucha clamping screw.

The socket as so far described is in principle essentially a standardsocket generally used on 110 volt circuits except that the slotscorresponding to the slots 48 and 50 have the same crosssectionaldimensions as the slot 50.

When the present socket is used for the lowest low voltage, say 6 volts,or is to receive a plug having only three terminals for two circuits ofdifferent voltages, the slot 48 can be as large as the slot 50 as noharm will result if the plug is reversed when entered in the socket, theconnection with the low voltage terminal merely not So far as thisinbeingmadeaswillbepresentlymadeclear. Since, however, it is desired toprovide but one socket for use on all lower voltage circuits, as 6volts, 12 volts, 32 volts, and in connection with plugs having more thanthree terminals and appliances having more than two circuits ofdifferent voltages, it is preferred to polarize the socket by making theslots 48 and4 50 with different cross-sectional dimensions. i

While only one of the contact ngers II, 52 will be energized when thesocket is used on the lower voltages, both fingers will be in mechanicalengagement with the terminal blades of the plug and will act .to holdthe plug mechanically rmly in place.

The socket is provided with a third terminal in addition to the twoterminals I and 52. To this end a contact plate SII is located in an endpart of a longitudinally elongated recess 62 located be- .tween theslots 48, 50 and extended substantially equally on opposite sides of thecenter of the socket. Said plate is held in place by a stud 84 rivetedor otherwise secured to the inner end of the contact plate and locatedin the center line of the socket and passed through an insulating boss86 projecting from the rear face of the wall 44, the stud having a wireconnector 68 on the end thereof. In the form illustrated in Fig. 5, theouter end of the contact plate 60 has an outwardly projecting contact orterminal member which is arranged to engage the third terminal I8 of theplug.

With the plug and socket as thus described 'the terminal member 10engages the plug terminal I8 and causes it to be moved inwardly of theplug body as the plug is inserted in the socket. Conncction is thusestablished with the particular low Avoltage circuit connected betweenthe terminal blade I6 and the third terminal I8.

In the plug and socket as illustrated in Figs. 4 and 7, the thirdterminal I8a projects from the end face of the plug and is adapted toengage the outer face of the contact plate of the socket, the contactmember 10 of Fig. 5 being omitted, and the third terminal yieldinginwardly of the plug body, as before, upon inserting the plug in thesocket. When such a plug is inserted in a standard III) volt socket,having no contact plate, the terminal I8a bears against the outer faceof the equivalent of the insulated Wall 44 and yields inwardly to permitthe plug terminals I4 and I6 to engage the socket terminals.

The purpose of the rim 46 is primarily to shield the contact member 10from accidental engagement. The rim can be omitted when desired.

In the furthermodiiied form of low voltage plug terminal as illustratedin Fig. 13 the terminal I8' isinset below the end face of the plug, thecompression spring 26a holding the contact face of the terminalyieldingly against the inner end of a bushing 21 xed within the outervend of the tube 20. Thus the ilexible conductor 24a. is relieved fromthe spring pressure which, for some purposes, is advantageous. A socketcooperating with such a plug terminal will have a suillciently long lowvoltage contact 10 to enter the bushing and engageand depress theterminal I8.

With an electrical appliance such as 35a, Fig. 12, having three circuitsor windings 12, 14, 16 of different voltages, the plug of Fig. 9 isused. Such a plug is similar to the plug of Fig. 1 except that it has afourth terminal I8b similar to the terminal I8 but disposed on theopposite side of the line through the blade terminals I4 and I8,

and the terminals I8, I8b and I4 being connected respectively to thelowest voltage winding 12, the intermediate voltage winding 14, and thehighest voltage winding 16, respectively.

Such a plug can be inserted in a standard 110 volt socket in either oftwo positions displaced 180 and establish connection only with the highvoltage winding 16 which usually will be designed for 110 volts. Theplug can be inserted-in the socket of Fig. 5 and will establishconnection only with the lowest voltage winding 12. For a socket toestablish connection with the intermediate voltage winding 14 thecontact plate 60 will be in the opposite end part of the recess 62, asindi- `cated by dotted lines, Fig. l0, so that the contact member 10will engage only with the fourth plug terminal I8b. The socket may haveappropriate markings 18, 18a at the opposite ends of the recess 62 toindicate the position of the contact plate for different voltages.

One socket type is common for all usual lower voltages and isconditioned for two diierent voltages by merely altering the position ofthe contact plate 60. This arrangement simplies and cheapens the cost ofthe socket since the users of the various voltages are commerciallydistinct and there is little danger that a builder of a Pullman car, forinstance, using 32 volts, would obtain and inadvertently install a 12volt socket intended primarily for use on the l2 volt systems ofairplanes.

It is thus apparent that the plug of the present invention can beinserted in a standard 110 volt socket and also in a special socket of adifferent voltage and will automatically establish connection only withthe proper circuit of the associated device.

The plug can be used also on a single circuit appliance when the circuitterminals are connected to the proper plug terminals as above described.Thus the appliance, say for 32 volts, can be plugged accidentally into110 volt socket without being damaged by being connected to the excessvoltage and yet will have its connections properly established whenplugged into the 32 volt socket.

I claim:

l. In combination with an electric power consuming device having aplurality of circuits of the terminal Ii being common to all windingsdiierent voltages, of a plug having terminals connected with saidcircuits arranged to enter different sockets energized at correspondingdifferent voltages and having cliierently positioned energizedterminals, and means constraining the plug to enter all sockets in thesame position and automatically connect the socket only with the circuitof the device adapted for the voltage of the socket.

2. In combination with an electric power consuming device having aplurality of circuits of dierent voltages, a plug having terminalsconnected with said circuits, and a socket having terminals energized atonly one of said different voltages, said terminals in said socket beingarranged to engage the terminals of said plug and automatically connectthe energized terminals of the socket only with the circuit of thedevice corresponding to the voltage of the energized socket terminals.

3. A multi-circuit plug adapted for cooperation with a standard voltsocket having a pair of spaced contact members and also with a secondsocket having a contact member in the position of one oi said pair ofcontact members and an-l gized at a different voltage from thev iirstsocket, said plug` comprising a body having a pair loi' terminal bladesenterable in both sockets and engageable with said pair of spacedcontact members, said plug having means which constrains its insertionin the second socket in a predetermined position only and having a thirdcontact member engageable in said predetermined Vposition of the plugwith Vthe last namedl contact member of said second socket andconstructed contact members and another contact member,

Y said second socket being energized at a different and arranged toadmit the eective insertion of said pair of terminals in said rstsocket.

.4s The combina-tion with an electric power consuming device having aplurality of windings of diierent voltages, one of the voltages beingadapted to be energized and operate satisfactorilyl when energized fromthe standard 110 volt house lighting circuit, a .plug adapted forcooperation with a standard 110 volt socket having a pair. of spacedcontact members and also adapted for cooperation with a second sockethaving a contact member in the position of one of said pairs oi' voltagefrom the standard socket, said plug comprising a body having terminalsconnected with the windings of said power consuming device, one pair ofsaid terminals comprising projecting terminal blades connected with thesaid 110 volt winding and enterable in both sockets and en-

